178 SPECIAL BACTERIOLOGY 



In Bouillon mixed with blood and spread out in a thin layer the 

 growth is somewhat abundant. 



Plate Cultures are useful for the isolation of the influenza for diagnostic 

 purposes. A little blood is added to the liquefied agar before it is 

 inoculated, or if Petri-dishes are used the agar is allowed to set and some 

 blood spread on the surface, and several stroke cultures made with the 

 diluted sputum. The developing colonies have the same appearance as 

 those in the agar tubes. 



The optimum temperature for the growth of the influenza bacillus is 

 37 to 38 C., the maximum limit is about 42 C., while the minimum 

 temperature is 26 to 27 C. At room temperature no growth takes 

 place. Oxygen is always necessary for the growth of the influenza 

 bacillus, while in presence of hydrogen and CO 2 with the addition of 

 blood to the media no growth is manifest. PfeifFer found that when he 

 used blood serum or blood fibrin instead of blood the results were 

 negative, and in further experiments he found that haemoglobin was 

 the necessary factor in the development of the influenza bacilli, as 

 haemoglobin agar was just as good a medium as blood agar. PfeifFer 

 also obtained positive results with the blood of rabbits, guinea-pigs, 

 pigeons, and fish, the growth with the pigeon blood being more 

 luxuriant and quicker than with human blood, owing to pigeon's blood 

 being very rich in haemoglobin. 



Vitality. Heated to 60 C. the influenza bacilli die in a few 

 minutes. At 43 C. they cease to grow ; they are not killed, for when 

 the tubes are again placed at 37 C. they again develop colonies. In 

 non-sterile drinking water the bacilli die in from twenty-four to thirty- 

 six hours. On blood agar and in bouillon they live for fourteen to 

 eighteen days, and in moist sputum they appear to retain their 

 infectivity. They do not resist drying very well. In blood or sputum 

 dried at 37 they are killed in one to two hours, and at room temperature 

 in thirty-six to forty hours. 



Pathogenesis. PfeifFer experimented with mice, rats, guinea-pigs, 

 rabbits, swine, cats, dogs, and monkeys ; and only in monkeys was he 

 able to produce a disease simulating influenza, by inoculating them 

 through the chest wall direct into the lungs, and also by what is a more 

 natural infection in one monkey, viz., by introduction of the influenza 

 culture into the nose. The disease manifested itself with fever and 

 slight coughing for several days ; an increase of the inoculated bacilli did 

 not occur. The introduction of large doses kills rabbits somewhat 

 quickly, the temperature falling rapidly before death ; it appears in those 

 cases to act as a poison, intoxication symptoms being manifested. Great 

 numbers of bacilli are found in rabbits inoculated intravenously. Dead 

 cultures mixed with chloroform act as a strong poison, a fact that tends 



